1. Field of the Invention
This invention relates to an automatic focus adjusting device suited for use in optical instruments such as cameras.
2. Description of the Prior Art
In the past, automatic focus adjusting devices have been proposed in various forms. These automatic focus adjusting devices were all designed to have the function to substitute for the double image coincidence type distance meter or the zone focus mark which had so far been developed. Therefore, the electronic circuit and control mechanism were both very complicated and as a result, in cameras, a price increase was required. On the other hand, earlier designs have either proposed or put into practical use a focus adjusting provision for the objective lens having fixed focus, or the so-called fixed focus camera. This fixed focus camera, when used in certain limited conditions (for example, outdoor photography under fine weather) brings forth very good results, but otherwise often provides an unsatisfactory result.